JPH07186031A - Spherical surface grinding method and device - Google Patents

Abstract

PURPOSE:To perform working equivalent to rough working to finishing working in a single process in sperical surface working in an electrolytic improcess dressing grinding method using a cup-shaped grinding wheel by forming a rough grinding wheel layer, a finishing grinding wheel layer, and a rough grinding wheel layer in this order from the inner side of a working surface of a grinding wheel. CONSTITUTION:A cup-shaped grinding wheel 2 having conductivity is formed in a three-layer structure comprising a rough grinding wheel layer 5, a finishing grinding layer 4, and a rough grinding layer 3 provided in this order from the inner side of its working surface. Its shape is formed in such a way that a forward end of the finishing grinding layer 4 is protruded from forward ends of the rough grinding layers 3, 5. The grinding wheel 2 and a work 1 are rotated, and grinding is performed while the work 1 is applied to the grinding wheel 2. Simultaneously as this, weak electricity coolant is supplied from a nozzle, and a voltage is applied between a minus electrode 6 and the processing surface of the grinding wheel 2 by a power source device through the weak electricity coolant. High precision spherical surface working can thus be performed in a single process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for spherically grinding a highly brittle material used as an optical element such as glass or ceramics by an electrolytic in-process dressing grinding method.

[0002]

2. Description of the Related Art FIG. 9 shows an electro-optical in-process dressing grinding method applied to spherical surface machining of an optical material.
This is the device described in Japanese Patent No. 43145. In the figure, the (+) pole of the electrolytic power supply 36 is electrically connected to the outer peripheral portion of the cup-shaped conductive grindstone 38 via the brush 37, and the (-) pole of the power supply 36 is the ground finish surface. The negative electrode 33 is formed in a shape similar to the curvature RA, and is arranged on the outer circumference of the chuck 32 so as to maintain a slight gap between the conductive grindstone 38 and the processed surface 31 in the spark-out process.
Connected with. Further, a nozzle 35 for supplying the weakly conductive coolant 34 is arranged in the gap between the processed surface 31 of the conductive grindstone 38 and the (-) electrode 33 by a coolant supply device (not shown).

In the above structure, the chuck 32 and the conductive grindstone 38 are rotated to bring the machined surface 31 into contact with the work 39 for grinding. At this time, a voltage is applied to the (−) electrode 33 and the brush 37 by the electrolytic power supply 36 while supplying the weakly electric coolant 34. As a result, the processing surface 31 is electrolytically dressed during processing and spherical surface grinding is performed.

[0004]

By the way, in order to obtain the surface roughness of a work as an optical element, it is necessary to perform several steps from roughing to finishing in ordinary grinding. This is because, in the grinding process, the smaller the grain size of the grindstone used for the working, the slower the workable speed, and the more likely the grindstone is clogged. That is, in the roughing process, a work is roughly created into a desired shape by using a low-mesh grindstone with a large mesh size and a low mesh. After that, a finishing process is performed by using a grindstone for finish grinding having a small grain size and a high mesh to obtain a desired surface roughness. In such a grinding process, since the finishing grindstone is easily clogged, it is necessary to further divide the finishing process into several steps and gradually finish the work to a desired surface roughness.

In the above-described conventional grinding apparatus, it is possible to continue processing from rough grinding wheels to finishing grinding wheels by electrolytic in-process dressing without clogging of the grinding wheels. Similarly, processing with a grindstone for rough grinding cannot obtain a processed surface roughness sufficient for use as an optical element. Further, when a grindstone having a small abrasive grain size is used for finishing the work, the processing speed is reduced. Therefore, in the conventional apparatus as well, in order to obtain the processed surface roughness of the work as the optical element, it is necessary to perform several steps of processing as in normal processing.

As described above, since the conventional apparatus requires a plurality of processing steps in order to obtain a high-quality machined surface, the number of steps is large, the processing is troublesome, and it takes a long time. is there. Therefore, it is an object of the present invention to provide a spherical grinding method and apparatus capable of performing processing corresponding to roughing to finishing in one step and in a short time.

[0007]

According to the spherical grinding method of the present invention, a cup-shaped grinding wheel that is driven to rotate is brought into contact with the surface of a work held by a rotatable work holder, and the electrolytic in-process dressing grinding method is used. In the method of performing spherical surface processing, a grinding wheel layer for rough grinding, a grinding wheel layer for finish grinding, and a grinding wheel layer for rough grinding are sequentially formed from the inside of the processing surface of the cup-type grinding wheel, and electrolytic dissolution of each layer of this cup-type grinding wheel is performed. By controlling the amount, it is possible to perform processing while maintaining a state in which the processed surface tip of the grinding wheel layer for finish grinding protrudes from the processed surface tips of other grinding wheel layers.

Further, the spherical grinding apparatus of the present invention comprises a rotatable work holder for holding a work and a cup-type grinding wheel which is driven to rotate while being in contact with the surface of the work, and electrolytic in-process dressing grinding is performed. In a device for performing spherical surface processing by a method, the cup-type grinding wheel is formed into a three-layer structure of a grinding wheel layer for rough grinding, a grinding wheel layer for finish grinding, and a grinding wheel layer for rough grinding in order from the inside of the processing surface, and electrolysis is performed. It is characterized by comprising means for independently controlling the amount of current flowing between the facing surface of the grindstone in the electrode for performing and the processed surface of each layer.

FIG. 1 shows a basic structure of the present invention, which is a work 1
The cup-shaped grinding wheel 2 is in contact with the surface of the workpiece in a rotationally driven state. The workpiece 1 is in the direction of arrow X, and the grinding wheel 2 is in the direction of arrow Y.
It can be moved in any direction. The grinding wheel 2 has a three-layer structure of a grinding wheel layer 5 for rough grinding, a grinding wheel layer 4 for finish grinding, and a grinding wheel layer 3 for rough grinding from the inside of the processed surface, and the tip of the grinding wheel layer 4 for finish grinding is rough ground. It is in a state of protruding from the tips of the grinding wheel layers 3 and 5. Further, electrolytic in-process dressing grinding is possible for the grinding wheel 2. In addition to this, the rough grinding wheel layer facing portion 7 and the finish grinding wheel layer facing portion 8 of the (-) electrode 6 for electrolytic in-process dressing are added.
Are independent of each other through the insulator 9 at the boundary portion,
This makes it possible to independently set the amount of current flowing at the tip of the machined surface of the rough grinding wheel layers 3 and 5 and the amount of current flowing at the tip of the machined surface of the finish grinding wheel layer 4.

FIG. 2 is a view of the grinding state of the present invention viewed from the grindstone axis direction to the work axis direction, and FIG. 3 is a sectional view taken along the line AA 'in FIG.

In the spherical surface machining in this case, as shown in FIG. 3, an outer surface a ₁ of the grindstone processed surface and an inner surface b _{2 of the} grindstone processed surface are used.
And processing by the bottom surface c of the grindstone processing surface are combined. That is, since the work 1 is rotated in the R ₀ direction and the cup-shaped grinding wheel 2 moves in the arrow Y direction or the work 1 moves in the arrow X direction, the work 1 is first processed on the whetstone outer peripheral portion a ₁ . Is grinded and subsequently grinded by the grindstone bottom surface c. Following this, the rotation of the work 1 in the R ₀ direction advances and simultaneously moves in the X direction or the Y direction. Therefore, machining by contact between the work 1 and the grindstone inner peripheral portion b ₂ and subsequent grindstone bottom surface c Also processed by. Further, after the cutting in the X direction or the Y direction is stopped, the machining (spark-out machining) is completed when the work 1 makes at least one revolution in the R ₀ direction.
The machined surface machined by the grindstone bottom surface portion c serves as a finish surface for grinding.

In the spherical surface machining, the grinding efficiency required for the machined surface per unit area of the grindstone is such that the side surfaces a and b of the grindstone are 2 to 6 times more efficient than the bottom surface c of the grindstone processed surface. It

Therefore, according to the above means, the inner and outer side surfaces of the grindstone, which requires high-efficiency machining during machining, are machined by the roughing grindstone, and the bottom surface of the grindstone, which acts on low-efficiency machining, is subjected to finish grinding. Since the finishing grindstone performs high-precision finishing, the surface roughness of the work after completion of machining becomes a highly-precision machined surface by the finishing grindstone.

Further, the amount of current flowing through the grinding wheel layer for rough grinding and the grinding wheel layer for finish grinding are set separately, and it is possible to control so that the electrolytic elution amount of each grinding wheel is optimal, so that the grinding surface of the grinding wheel layer for rough grinding is applied to The protrusion amount of the processing surface tip of the grinding wheel layer for finish grinding is always maintained stable, and stable and highly accurate spherical surface processing can be performed in one process.

[0015]

First Embodiment FIG. 4 shows a processing apparatus according to the first embodiment of the present invention. The work 10 is held by a holder 11 and is rotatable about a rotation C by a driving device (not shown). The grinding wheel 12 is rotatable about a rotation axis B by a driving device (not shown) via a spindle 23.

The processed surface of the grinding wheel 12 having conductivity is
Abrasive grains such as diamond powder and metal powders such as Cu, Sn, and Fe are mixed and composed of a heat-treated sintered alloy, and the middle ring zone is formed by a high-mesh (# 4000) grinding wheel 13 for finish grinding. At the same time, the inner and outer sides of the finishing grinding wheel portion are formed by the low-mesh (# 400) rough grinding wheel 14, and the tip of the processing surface of the finishing grinding wheel is the processing of the rough grinding wheel. It projects 4 to 15 μm with respect to the tip of the surface.

The movement of the work 10 in the arrow X direction and the movement of the spindle 23 in the arrow Y direction can be arbitrarily set and moved by a driving device (not shown). The (+) electrode of the power supply device 15 provided outside the device is electrically connected to the outer peripheral portion of the grinding wheel 12 via the brush 16.
(−) The facing portion 18 of the grindstone for the rough grinding and the facing portion 19 of the grindstone for the finish grinding of the electrode 17 are insulated from each other on the boundary line.
Since it is independent via 0, it is possible to independently set the amount of current flowing at the tip of the machined surface of the rough grinding wheel 14 and the amount of current flowing at the tip of the machined surface of the finish grinding wheel 13. 21 is a coolant supply device (not shown)
It is a nozzle for supplying the weak electric coolant 22 to the processing area. Grinding with this processing device
And the work 11 is rotated to move the work 11 in the direction of the arrow X,
Alternatively, the work piece 10 is brought into contact with the grinding wheel 12 by moving the spindle 23 in the direction of the arrow Y, and at the same time, the weak electric coolant 22 is supplied from the nozzle 21 and the (−) electrode 17 is supplied by the power supply device 15. A voltage is applied between the machined surface of the grinding wheel 12 and the machined surface of the grinding wheel 12 via the weakly electric coolant 22.

According to this embodiment, the machined surface of the grinding wheel 12 is always stably dressed, and at the same time the rough grinding wheel 14 is used.
Since the protrusion amount of the tip of the work surface of the finish grinding grindstone 13 relative to the tip of the work surface is constantly maintained, it is possible to stably perform highly efficient and highly accurate spherical surface machining in one step. is there. Further, in the present embodiment, various finishing surfaces can be obtained by selecting a combination of the finishing grinding wheel and the rough grinding wheel mesh according to the finish surface roughness of the workpiece to be sought.

[0019]

[Embodiment 2] FIG. 5 shows a grinding apparatus according to Embodiment 2 of the present invention. The same members as those in Embodiment 1 are designated by the same reference numerals, and the description thereof will be omitted.

In this embodiment, a step is provided at the boundary between the surface of the (-) electrode 24 facing the processed surface of the rough grinding wheel 14 and the surface facing the processed surface of the finish grinding wheel 13. Further, unlike the first embodiment, the (-) electrode has an integral structure and is connected to the (-) pole of the electrolytic power supply 25.

According to the present embodiment, by providing the step on the (-) electrode, the distance between the (-) electrode and the respective processed surfaces of the rough grinding wheel and the finish grinding wheel can be individually set. It is possible. Therefore, since the electric resistance between the (-) electrode and each grindstone processing surface can be set separately, it is possible to set the electrolytic current amount that matches the required electrolytic dressing amount of each grindstone. Therefore, the machined surface of the grinding wheel is always stably dressed, and at the same time, the protrusion amount of the machined surface tip of the finishing grinding wheel relative to the machined surface tip of the rough grinding wheel is a simple configuration of (-) electrode shape setting. Because it is stably maintained at
It is possible to stably perform highly efficient and highly accurate spherical surface machining in one process.

[0022]

[Third Embodiment] FIG. 6 shows a grinding apparatus according to a third embodiment of the present invention, and FIG. 7 shows a view of the (-) electrode arrangement portion in the present embodiment as seen from above the processing surface of the grinding wheel. In this embodiment, the same members as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, the area of the portion of the (-) electrode 26 facing the processed surface of the finish grinding wheel 13 is larger than the area of the portion of the rough grinding wheel 14 facing the processed surface. According to the present embodiment, since the shape of the (-) electrode is simpler than that of the processing apparatus of the second embodiment, it is possible to easily dispose the (-) electrode and the respective grindstones. Since the area of the (−) electrode facing to (1) can be set so as to maintain the optimum dressing amount,
Similarly to the above, it is possible to stably perform highly efficient and highly accurate spherical surface machining in one step.

[0023]

Fourth Embodiment FIG. 8 shows a grinding apparatus according to a fourth embodiment of the present invention. The same members as those in the first and second embodiments are designated by the same reference numerals and the description thereof will be omitted.

The processed surface of the grinding wheel 30 having conductivity is
Abrasive grains such as diamond powder, metal powders such as Cu, Sn, and Fe, and a non-conductive resin material are mixed and composed of a heat-treated sintered alloy. Of the fine grinding particles and a large amount of resin material for finishing grinding (# 4000) 29, and the inner and outer sides of the finishing grinding stone have a particle diameter of 35 μm.
Rough grinding stone containing a large amount of coarse abrasive grains and metal powder (# 4
00) 28.

Therefore, the grindstone 28 for rough grinding containing a large amount of metal powder has higher conductivity than the grindstone 29 for finish grinding. The tip of the processed surface of the grindstone 29 for finish grinding is 4 to 4 times the tip of the processed surface of the grindstone 28 for rough grinding.
It projects by 15 μm.

According to the present embodiment, the conductivity of the rough grinding wheel 28 and the finishing grinding wheel 29 can be freely set at the time of manufacturing the grinding wheel. Therefore, compared with the second and third embodiments, the shape of the (-) electrode is special. Even if it is not formed into a different shape, a grinding wheel 29 for finish grinding is applied to the tip of the processing surface of the grinding wheel 28 for rough grinding by electrolytic action.
It is possible to optimally maintain the protrusion amount of the processed surface tip.
Therefore, similarly to the first embodiment, it is possible to stably perform highly efficient and highly accurate spherical surface machining in one step.

As described above, according to the present invention, it is possible to perform high-precision grinding of spherical surfaces of optical elements and the like in one step in a short time, thus shortening the processing cycle time and the number of steps. Is possible.

[Brief description of drawings]

FIG. 1 is a partially cutaway side view of the basic configuration of the present invention.

FIG. 2 is a plan view showing a grinding method of the present invention.

FIG. 3 is a sectional view taken along the line AA ′ of FIG.

FIG. 4 is a partially cutaway side view of the first embodiment.

FIG. 5 is a partially cutaway side view of the second embodiment.

FIG. 6 is a partially cutaway side view of the third embodiment.

FIG. 7 is a plan view of an electrode portion of Example 3.

FIG. 8 is a partially cutaway side view of the fourth embodiment.

FIG. 9 is a side view of a conventional device.

[Explanation of symbols]

 1 Work 2 Grinding Wheel 3 Grinding Wheel Layer for Rough Grinding 4 Grinding Wheel Layer for Finishing Grinding 5 Grinding Wheel Layer for Rough Grinding 6 Electrode 9 Insulator

Claims (2)

[Claims] 1. A cup-type grinding wheel which is driven to rotate is brought into contact with a surface of a work held by a rotatable work holder,
In the method of performing spherical surface processing by electrolytic in-process dressing grinding method, a grinding wheel layer for rough grinding, a grinding wheel layer for finish grinding, and a grinding wheel layer for rough grinding are sequentially formed from the inside of the processing surface of the cup-type grinding wheel, and this cup type is used. A spherical grinding method characterized by performing machining while maintaining a state in which the processed surface tip of the grinding wheel layer for finish grinding protrudes from the processed surface tips of other grinding wheel layers by controlling the electrolytic dissolution amount of each layer of the grinding wheel. . 2. A device for performing spherical surface machining by an electrolytic in-process dressing grinding method, comprising a rotatable work holder for holding a work, and a cup-type grinding wheel that is driven to rotate while being in contact with the surface of the work. In the above, the cup-type grinding wheel is formed into a three-layer structure of a grinding wheel layer for rough grinding, a grinding wheel layer for finish grinding, and a grinding wheel layer for rough grinding in order from the inside of the processed surface, and the grinding wheel of the electrode for performing electrolysis is A spherical grinding machine comprising means for independently controlling the amount of current flowing between the facing surface and the processed surface of each layer in each layer.